Great answer, @biologghe, thanks for helping out 
@SusanD If you think there is a problem with a GTN tutorial (from here: https://training.galaxyproject.org/), please scroll down to the bottom of it and submit a feedback form explaining what seems wrong. We review those and make fixes/enhancements based on cumulative reports of issues/confusion.
We could also vet that first here if the tutorial/example data versus your data is confusing. Post back a link to the tutorial section where this is covered, note the tool and input, and I’ll quickly review/provide some feedback myself or recruit some feedback from the tutorial author(s) if it is unclear to me too.
If the tutorial is from a different source than the GTN, you might want to reach out to the authors and explain what is confusing, so they can clarify or make updates.
Thanks!
Update: Looks like you’ve moved this to a new thread, can follow up there: Failed to use "Scater: plot library QC"